package example;
 
import java.io.IOException;
import java.util.StringTokenizer;
 
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
 
public class WordCount {
 
  public static class TokenizerMapper 
       extends Mapper<Object, Text, Text, IntWritable>{
 
    private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();
 
    public void map(Object key, Text value, Context context
                    ) throws IOException, InterruptedException {
      StringTokenizer itr = new StringTokenizer(value.toString());
      while (itr.hasMoreTokens()) {
        word.set(itr.nextToken());
        context.write(word, one);
      }
    }
  }
 
  public static class IntSumReducer 
       extends Reducer<Text,IntWritable,Text,IntWritable> {
    private IntWritable result = new IntWritable();
 
    public void reduce(Text key, Iterable<IntWritable> values, 
                       Context context
                       ) throws IOException, InterruptedException {
      int sum = 0;
      for (IntWritable val : values) {
        sum += val.get();
      }
      result.set(sum);
      context.write(key, result);
    }
  }
 
  public static void main(String[] args) throws Exception {
	  args = new String[] {"hdfs://localhost:9000/ex1/input","hdfs://localhost:9000/ex1/output"}; 
	  Configuration conf = new Configuration();
	  conf.set("fs.defaultFS",  "hdfs://localhost:9000");
	  String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
	  if (otherArgs.length != 2) {
		  System.err.println("Usage: wordcount <in> <out>");
		  System.exit(2);
	  }
	  Path path =new Path(args[1]);
      //加载配置文件 
      FileSystem fileSystem = path.getFileSystem(conf); 
      //输出目录若存在则删除 
      if (fileSystem.exists(new Path(args[1]))) { 
      	fileSystem.delete(new Path(args[1]),true); 
      }
	  Job job = new Job(conf, "word count");
	  job.setJarByClass(WordCount.class);
	  job.setMapperClass(TokenizerMapper.class);
	  job.setCombinerClass(IntSumReducer.class);
	  job.setReducerClass(IntSumReducer.class);
	  job.setOutputKeyClass(Text.class);
	  job.setOutputValueClass(IntWritable.class);
	  FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
	  FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
	  System.exit(job.waitForCompletion(true) ? 0 : 1);
  }
}
